单叶血藤胚胎学研究Ⅱ--大孢子发生及雌配子体发育

目的 观察研究大血藤属植物单叶血藤(Sargentodoxa simplicifolia)外形上的两性花中大小孢子发生和雌雄配子体的发育过程，为大血藤属植物胚胎学研究积累资料，并为其系统分类及保护生物学提供胚胎学依据。方法 石蜡切片、半薄切片、Laica DMLB显微镜观察并摄影。结果 单叶血藤心皮多数、离生，每室具胚珠一枚。边缘胎座、倒生胚珠、双珠被、厚珠心、珠孔仅由内珠被形成，珠心表皮参与珠心组织的形成。大孢子母细胞减数分裂产生T-形四分体和少数线形四分体。部分二分体中仅合点端细胞进行减数分裂Ⅱ，而珠孔端二分体细胞尚未分裂就退化，最后合点端的大孢子发育为雌配子体。外形上的两性花中的雄蕊早期发育正常，但同一小孢子囊中的小孢子母细胞减数分裂不同步；大部分小孢子只发育到单核靠边期，少数小孢子能发育成二细胞花粉粒；花药壁始终不开裂。结论 单叶血藤雌配子体发育为单孢子蓼型，该外形上的两性花是一种较为原始的雌花。

A study on the embryology in Sargentodoxa simplicifolia Ⅱ: Megasporogenesis and female gametes development

Aim The development of megasporogenesis and microspore of morphological bisexual flowers of S. simplicifolia was studied in order to discover detail information of embryology of Sargentodoxa and to provide embryonic proofs for its classification.Methods Methods of Paraffin section and semithin section were adopted and all slices were observed and took photos under Laica DMLB microscope.Results The gynoecium is polycarpellary and apocarpous. The ovary shows marginal placentation bearing only one ovule, which is anatropous bitegmic and crassinucellate with well developed parietal tissue formed also by pariclinal divisions of the nucellar epidermis. The megaspore mother cell undergoing meiotic divisions produces a T-shaped, or, rarely, linear tetrad. While the micropylar dyad sometime remains undivided. female gametes develop from the chalazal megasporogenesis. In the stamen of the morphological bisexual flowers, the meiotic divisions of the microsporocytes in the same microsporangium were not simultaneous and most of the microspore developed up to the uninucleate pollen grain stage. The anthers were never dehiscent.Conclusion The development of the embryo sac of S. simplicifolia conforms to the Polygonum type. The morphological bisexual flowers are primitive female flowers. Sargentodoxaceae is acceptable.